Sealed casing for containing an electric accumulator

ABSTRACT

A sealed casing is provided for withstanding a certain pressure. The casing contains an electric accumulator, and is formed by at least one wall which has at least one closing area formed by a plastic band for connecting two edges of the wall. The closing area includes an adhesive part and a shiftable part to form an effective and economical closure.

BACKGROUND OF THE INVENTION

The invention relates to a sealed casing provided for withstanding acertain pressure and intended to contain notably an electricaccumulator, the casing being formed by at least one wall which has atleast one closing area formed by a plastic band for connecting two edgesof the wall.

The invention also relates to a flat accumulator formed from such acasing.

The invention finds highly significant applications, for example, forcontaining an accumulator of the lithium-ion or lead-acid type.

U.S. Pat. No. 5,326,652 describes such an accumulator and its casing.However, in that document, the problem of internal pressure of theaccumulator is not mentioned. Indeed, the accumulators create pressuresinside the envelopes formed by the casings containing them. Thispressure may sometimes be so high that the envelope explodes, which isvery dangerous, above all if the accumulator is of the type containinglithium. Therefore, valves may be provided which open when the variationof pressure exceeds a certain value that is incompatible with thesolidity of this envelope.

SUMMARY OF THE INVENTION

The present invention proposes a casing of the type defined in theopening paragraph, the casing having an effective and low cost valvewhich can be incorporated notably in ultraflat casings.

Therefore, such a casing is characterized in that the closing areacomprises an adhesive part and a shiftable part.

Thus, thanks to the invention, when the pressure is too large, theshiftable part which is not fixed to the edges of the wall may shift andleave an opening, so that the gas creating excessive pressure canescape.

According to a first characteristic feature of the invention, the lengthof the shiftable part is such that said shiftable part comes loose fromsaid edges under the influence of an excessive pressure, thus creatingan opening to the exterior.

The elasticity of this shiftable part is sufficient so that when thepressure becomes normal again, the part reassumes its natural position.The operation of the inside element is re-established.

According to a second characteristic feature of the invention, at leastone opening to the exterior of said plastic casing is provided at thelevel of said edges and the length of the shiftable part is such thatunder the influence of excessive pressure the opening is brought intocontact with the exterior of said casing after the band has shifted.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows in an exploded view a casing according to the invention,

FIG. 2 shows an elevational view of the opening area,

FIG. 3 shows the deformation of the band under the influence ofpressure,

FIG. 4 shows a variant of a preferred embodiment of a casing accordingto the invention,

FIG. 5 shows the deformation of the band,

FIGS. 6A-6B show a second variant of an embodiment,

FIGS. 7A-7B show a third variant of an embodiment of the invention,

FIGS. 8A-8B show a fourth variant of an embodiment of the invention, and

FIG. 9 shows a flat accumulator formed on the basis of a casing, allthis in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 is shown a casing of cylindrical form. It is formed by a sidewall 1 formed by a curved plate, so that it has a cylindrical form. Acap 3 blocks the upper part of the cylinder, whereas a base 5 blocks thelower part. This plate 1 has two edges 8 and 9 which, as a result of theplate being curved, come in each other's proximity and overlap eachother. For connecting these edges, a closing area 10 is provided in thepart situated inside this overlap formed, in essence, by a silicon-basedresin band 11. This area is to be such that when the cap 3 and the base5 are put in place, the sealing of the casing thus formed is to beensured. The casing is also to be able to withstand a certain internalpressure.

According to the invention, this closing area 10 has an adhesive part12A and 12B and a shiftable part 13. In FIG. 1, the shiftable part 13 issituated between two adhesive parts 12A and 12B. This is shown in moredetail in the cross-sectional view along C of FIG. 2. The adhesive part12 is the part for which the plastic band 11 is solidly stuck on saidedge 8 and 9, either by its natural adhesion, or by glue or also byultrasound soldering. The shiftable part is not stuck to the edges atall, or stuck only slightly. This may be realized by a teflon coating.This shiftable part 13 remains tighented and, locked between the twoedges 8 and 9 by the natural position of the elastic shiftable part 13.

In FIG. 2 are shown in bold lines the places where the adhesion betweenthe band and the edges exists. With respect to area 12A, the bold lines15A and 16A show the adhesion between the band 11 and the edges 8 and 9,respectively. As regards the adhesive area 12B, the bold lines 15B and16B show the adhesion between the band 11 and the edges 8 and 9,respectively.

FIG. 3 shows the behavior of the closing area 10 when the internalpressure of the casing becomes excessive. Under the influence of thispressure, the shiftable part no longer ensures that the band 11 is heldin place. It is shifted to the exterior, so that an opening 15 is formedconnecting the inside of the casing with the outside. The purpose ofthis is to reduce the pressure on the inside. Depending on the materialof the band, this shift may be final or not. In the first case, thecasing is thus to be replaced, and in the second case the band resumesits initial position due to its elasticity and the casing ensures itsfunction.

FIG. 4 shows the preferred embodiment of a casing according to theinvention. It is formed by two plates 20 and 21 opposite each other andconnected by the band 11 which is placed along the periphery of thesetwo plates 20 and 21. The casing shown in FIG. 4 is similar in form tocommonly used credit cards. As a matter of fact this casing is intendedto contain lithium-ion or lead-acid battery elements and/or to be of atype described in U.S. Pat. No. 5,326,652 mentioned above. The casing ofFIG. 4 thus comprises in accordance with the invention a shiftable part13 which may be deformed under the influence of pressure and may let gasthat causes this excessive overpressure escape by creating an opening 15as shown in FIG. 5.

FIGS. 6A-6B show another embodiment of the invention. According to thisother embodiment, at least one opening 35 is provided on the edge andone of the plates 20 or 21 or even in the two. Under normal pressure,this opening is masked by the band 11, or is located outside theenvelope and does not let gas escape. This is shown in FIG. 6A. When thepressure becomes too high, under the influence of the pressure, the bandis deformed at the level of area 13, and the opening 35 is unmaskedletting the excessive gas escape. This is shown in FIG. 6B.

FIGS. 7A-7B show another embodiment. In this Figure, the band isintersected by a sealed slot 45 or a gap at the level of the shiftablepart. The sealing is thus ensured as this is shown FIG. 7A. Under theinfluence of pressure, the part(s) situated on either side of theintersection of the shiftable part is or are pushed outward, thusletting the surplus gas escape, as is shown at FIG. 7B.

A last embodiment is shown in FIGS. 8A-8B. The material which forms thecasing is a deformable material, so that it is deformed in the case ofoverpressure. Due to the internal overpressure, the deformable casing 20is no longer maintained against the shiftable area 13 and deforms toform an opening 35' (see FIG. 8B) which and lets the gas escape.

FIG. 9 shows in an exploded view an accumulator according to theinvention. It is formed by a flat casing of the type shown in FIG. 3 andfollowing and by an accumulator element 50 of the type described incited Patent. The electrodes of this element are accessible via theplates 52 and 54 which are covered by the band 11 so as to ensure thesealing.

What is claimed is:
 1. A sealed casing for an accumulator comprising:awall which encloses said accumulator; and a sealing band which sealsedges of said wall; said sealing band having a fixed part which isfixedly attached to said edges, and a non-fixed part which contacts saidedges without being fixedly attached to said edges; said sealing bandcontacting said edges to isolate an interior of said casing from anexterior of said casing; said non-fixed part having an elasticity thatprovides sealing of said sealed casing in a quiescent condition.
 2. Thesealed casing of claim 1, wherein said wall is curved to form acylinder.
 3. The sealed casing of claim 1, wherein said sealing band isformed between overlapping parts of said edges.
 4. The sealed casing ofclaim 1, wherein said non-fixed part deforms toward said exterior toexpose said interior to said exterior during overpressure which occurswhen an internal pressure is greater than an external pressure.
 5. Thesealed casing of claim 1, wherein said non-fixed part covers a hole insaid wall in said quiescent position and deforms to uncover said holeand expose said interior to said exterior during overpressure whichoccurs when an internal pressure is greater than an external pressure.6. The sealed casing of claim 1, wherein said wall deforms to create anopening at said non-fixed part to expose said interior to said exteriorduring overpressure which occurs when an internal pressure is greaterthan an external pressure.
 7. The sealed casing of claim 1, wherein oneside of said non-fixed part is not fixedly attached to said fixed partso that said one side moves toward said exterior to expose said interiorto said exterior during overpressure which occurs when an internalpressure is greater than an external pressure.
 8. A casing comprising:afirst plate; a second plate; and a sealing band located between saidfirst plate and said second plate at edges of said first plate and saidsecond plate wall, said sealing band contacting said edges to isolate aninterior of said casing from an exterior of said casing, wherein saidsealing band has a fixed part which is fixedly attached to said edges,and a non-fixed part which is not fixedly attached to said edges; saidnon-fixed part having an elasticity that provides sealing of said sealedcasing in a quiescent condition.
 9. The casing of claim 8, wherein saidfirst plate and said second plate are flat.
 10. The casing of claim 8,wherein said non-fixed part deforms toward said exterior to expose saidinterior to said exterior during overpressure which occurs when aninternal pressure is greater than an external pressure.
 11. The casingof claim 8, wherein said non-fixed part covers a hole in said wall in aquiescent position and deforms to uncover said hole and expose saidinterior to said exterior during overpressure which occurs when aninternal pressure is greater than an external pressure.
 12. The casingof claim 8, wherein said first plate deforms to create an opening atsaid non-fixed part to expose said interior to said exterior duringoverpressure which occurs when an internal pressure is greater than anexternal pressure.
 13. The casing of claim 8, wherein one side of saidnon-fixed part is not fixedly attached to said fixed part so that saidone side moves toward said exterior to expose said interior to saidexterior during overpressure which occurs when an internal pressure isgreater than an external pressure.
 14. An accumulator comprising:acasing; and a battery element located in said casing; wherein saidcasing includes:a wall which encloses said battery element; and asealing band which seals edges of said wall; said sealing band having afixed part which is fixedly attached to said edges, and a non-fixed partwhich is not fixedly attached to said edges; said sealing bandcontacting said edges to isolate an interior of said casing from anexterior of said casing; said non-fixed part having an elasticity thatprovides sealing of said sealed casing in a quiescent condition.
 15. Theaccumulator of claim 14, wherein said wall is curved to form a cylinder.16. The accumulator of claim 14, wherein said wall is flat and includesa first plate and a second plate which are sealed at said edges by saidsealing band.
 17. The accumulator of claim 14, wherein said sealing bandis formed between overlapping parts of said edges.
 18. The accumulatorof claim 14, wherein said non-fixed part deforms toward said exterior toexpose said interior to said exterior during overpressure which occurswhen an internal pressure is greater than an external pressure.
 19. Theaccumulator of claim 14, wherein said non-fixed part covers a hole insaid wall in a quiescent position and deforms to uncover said hole andexpose said interior to said exterior during overpressure which occurswhen an internal pressure is greater than an external pressure.
 20. Theaccumulator of claim 14, wherein said wall deforms to create an openingat said non-fixed part to expose said interior to said exterior duringoverpressure which occurs when an internal pressure is greater than anexternal pressure.
 21. The accumulator of claim 14, wherein one side ofsaid non-fixed part is not fixedly attached to said fixed part so thatsaid one side moves toward said exterior to expose said interior to saidexterior during overpressure which occurs when an internal pressure isgreater than an external pressure.